Altered Beast (獣王記 Jūōki?, lit. "Beast King's Chronicle") is a 1988 beat 'em up arcade game developed and manufactured by Sega. The game is set in Ancient Greece, and follows a centurion who is resurrected by Zeus to rescue his daughter Athena, and to do so becomes able to turn into beasts such as the werewolf with the use of power-ups. After its initial arcade release, it was ported to several home video game consoles and home computers, including the Sega Mega Drive and Sega Genesis, for which it was a pack-in game. This ultimately led to the Sega Genesis being shipped with Sonic the Hedgehog instead. The primary designer was Makoto Uchida, also responsible for the creation of Golden Axe.
Altered Beast is a side scrolling, platform, beat 'em up game. The player controls the centurion, fighting undead creatures and monsters in a setting resembling Ancient Greece, with originally five levels, in a graveyard, the Underworld, a cavern, Neff's palace and base at the city of Dis. One of the enemies, a white two-headed wolf (blue in the Mega Drive version, and a blue ox in the DOS version) upon defeat releases a Spirit Ball, a power-up orb which increase the strength and size of the player character. Three orbs turn the centurion into a beast, which in the original version were a werewolf, a thunder weredragon, a werebear, a weretiger, and the more powerful golden werewolf (other beasts can be seen in the Japanese Famicom version and the Game Boy Advance version). Each beast has its own abilities, such as the dragon's flight and lightning, and the bear's petrification. After becoming the beast, the character can face the end-level boss, which upon defeat causes Neff to appear and remove the transformation orbs.
A Roman centurion who had died in battle is resurrected from the dead by Zeus. The centurion is ordered by Zeus to save his daughter Athena from a Demon God called Neff in the Underworld. To become able to withstand the perils, the warrior gets the ability to absorb spirit balls which transform him into an Altered Beast, a part animal, part human creature of formidable force. Between each level are small animations giving the player glimpses of Athena's peril.
In its initial arcade release, Altered Beast was a well-received game. Its conversion to the Sega Mega Drive was considered inferior to the arcade in terms of sprite quality. However, the Sega Mega Drive version was actually more advanced than the arcade version in one regard – its utilization of parallax scrolling. Mega placed the game at #1 in their list of the 10 Worst Mega Drive Games of All Time. Its re-release for the Wii's Virtual Console was given a lukewarm reception by GameSpot and IGN, describing the game as merely decent with some nostalgic value. The Xbox Live Arcade re-release was even described by IGN as "relic of the arcade heyday that just doesn't hold up today".